1. Field of the Invention
This invention relates to syringe systems that are used for extruding materials therefrom, and more particularly to a dental syringe system which more easily provides the potential for separated, more controllable doses of a solid but pliable extrudent as the material is extruded from the syringe system, the material being a light activating composite which cures with exposure to an activating light.
2. Prior State of the Art
The prior art addresses syringes which are constructed to progressively extrude solid, yet pliable materials such as composite materials that are used in clinical dental procedures. The extrudent in dental procedures may be a light-cured composite material. Once the material is extruded from the syringe, it must be moved to the site where the material is to be applied. The material may be extruded directly onto an application site by contacting the site directly with the tip of the syringe. However, such direct placement may cause contamination of a large portion of the material when the application site is unsterile. Thus, direct application is not the best means of application of the extruded material where concern for cross contamination exists and adequate safeguards aren't present.
For the purposes of illustrating the technology of tooth restoration, FIGS. 8 and 9 are featured to show respectively a top tooth and a bottom tooth, 80 and 90, with respective teeth restoration areas 82, and 92, which are to be treated or filled with composite materials.
Typical of dental tooth filling composite materials is their common propensity to shrink while curing or hardening after application to a tooth restoration site, 82, 92. Due to the predictable degree of shrinkage, the dentist must build up the tooth restoration areas, 82, 92, in incremental steps or layers. As shown in FIGS. 8 and 9, the areas to be treated or filled are individual tooth surfaces, such as surfaces 84 and 86 at tooth restoration site 82 on an upper jaw tooth 80, and such as surfaces 94 through 98 at tooth restoration site 92 on a lower jaw tooth 90.
Filling a tooth restoration site, 82, 92, often involves small amounts of composite material. Even when a restoration site is relatively large, small, controllable amounts of the material are preferably used for the application of a layer of light-cured composite material, B, that has been extruded from a syringe, C, (See FIGS. 1A and lB) and then carefully shaping the layer on and around a prepared tooth surface. The shaped composite material is then exposed to an activating light, D, to instigate the curing and shrinking process of the shaped layer of composite material.
The process of shrinking must be allowed to proceed before applying yet another layer of extruded composite material to the same tooth. The need for sequential layering is understood by those of skill in the art in that with certain preferred bonding agents there is enough adhesion of the dental composite material to the walls of the preparation area, (82, 92) that if the dentist were to apply in a single application the total mass required to fill the preparation area, (82, 92) the material would adhere to both the buccal side and the lingual side of the preparation area, (82, 92) and would then contract the tooth (80, 90) and would tend to pull the cusps of the tooth together causing moderate to extreme post operative discomfort and sensitivity in the tooth (80, 90), as well as other potential side effects therefrom such as premature failure of the restoration. However, by layering the material as shown at layers 86a-86b or 95a-95d in progressive steps and at various angles at which the layers of the extrudent are applied, the drawing or pulling of the cusps together in an uncontrolled shrinkage process will be prevented.
The dentist must properly account for the shrinkage of each layer of the composite material that is applied. Restoration sites, 82, 92, incrementally restored in small layers, will cause the mass of composite material applied thereat to incrementally shrink across the respective smaller layered areas until the dentist has built up the restoration site, 82, 92 to the desired surface morphology of the tooth, 80, 90.
An added benefit of the incremental layering process is the assurance that even the deepest layers of the restoration sites, 82, 92, have an adequate degree of exposure to activating light to cure and shrink properly.
As shown in Prior Art FIGS. 1A and 1B, the dental tool, E, that is used to remove the extrudent, B, from the syringe, C, may be a shaping tool. The shaping and/or placement tool or instrument could be an instrument of any design that is comfortable for the dentist to use. For instance, a spatulating device may be used for applying the material, B, onto a flat surface such as those surfaces shown in FIGS. 8 and 9. The tool could also be a little round section condenser or plugger which is used to place the composite material, by pushing on the end of the tool, into a deeper tooth preparation site such as on a posterior back tooth.
Tools having a cross-sectional area that is cylindrical, such as are used in packing dental composite material into tooth preparation areas, may be clumsy when also used to dig dental composite material out of the end of a syringe. They may also be clumsy for both retaining the material on the operative end of that instrument and then packing it into the bottom of the tooth restoration site. Tools that are not suited for such digging operations, in addition to being somewhat clumsy, tend to be wasteful of the composite material and can incorporate air voids into the material in the process of digging, a detriment which is discussed below.
Using cylindrical, cross-sectional tools to dig out or remove material from a syringe barrel is also undesirable in that many times the pieces of composite material that are thus removed from the syringe are of an irregular shape, such as long, skinny, or strung-out pieces. By the time the resultant irregular shape is approximated over the tooth restoration site and packed in, the material may have incorporated air bubbles or voids, or may inadvertently contact undesired areas such as unprepared tooth surfaces, gum tissue or the like. A further disability is that such irregular pieces of composite material are quite clumsy to precisely place at the tooth restoration site.
As is best seen in Prior Art FIG. 1-A, a spatula, E, is used to remove material from a syringe, C, which the dentist (I) is holding. An assistant or the dentist may also be holding a mouth mirror in one hand. The syringe, C, may require two hands to operate when extruding the composite material, B, because the material, B, is solid enough that many prior art syringes used have a threaded plunger, H, to help extrude the material, B. As the shaping and/or placing tool, E, is manually manipulated to remove the composite material, B, out of the inside of the syringe, C, it is difficult to get predictable quantities of composite material, B, properly situated at the end of instrument, E. In fact, it is not uncommon for masses of the composite material, B, so excavated, to be dropped to the floor of the dental procedure room, and to be thus wasted.
Where the composite material, B, is a light-cured material, the dental assistant, A, will simultaneously try to manually cover the material, B, with the other hand, G, or with a finger or fingers of the same hand, to protect it from activating light, D, radiated from a light source. Such protection is desirable to protect the portions of the material, B, which are not to be removed, from a premature curing process. However, this protective effort by the dental assistant, A, to cover the material, B, is a problem in that the assistant's hand, G, is not free for other and simultaneously required tasks.
In Prior Art FIG. 1A, the dentist, I, digs at the material, B, with a spatula, E, from the inside of the syringe, C, in order to form a mound of the substance material, B, on the end of the instrument, E. A problem with this procedure is that the digging of the material, B, with the instrument, E, tends to interstitially place air bubbles or voids in the material, B. The incorporated air into the composite material, B, will in turn be passed on in the material, B, when it is placed in the preparation site, 82, 92, and could potentially thus degrade the strength or other desired properties of the composite of the restoration.
As shown in Prior Art Figure 1B, the material, B, extends beyond the end of the syringe, C. In such circumstances, the dentists need not dig within the syringe, C, to acquire the necessary mound of the material, B, on the instrument, E. However, such a mound of material, B, may be large, unwieldy, and uncontrollable as the dentist begins to sever the mound with the instrument, E. Even the slightest of misdirection of the instrument, E, may cause the material, B, to become dislodged and fall onto the floor or into the dental patient's bib.
The dentist, I, in order to obtain better control between the instrument, E, and the extrudent mound, B, may use a finger, F, to steady the mound, B, as shown in Prior Art FIG. 1B. Once so held, and in order to obtain a desired and predictable amount of extrudent on the instrument, E, the dentist, I, severs a wedge of the extrudent material, B, with the instrument, E, using a surface of the finger, F, as a cutting surface for the instrument, E, to pinch against.
Using the finger, F, in the procedure potentially provides a ready source of contamination which is in turn carried with the material, B, to the application site, 82, 92. Also, the instrument, E, may have edges which are sharp enough to lacerate or puncture the gloved finger, F, in which case the dental assistant, A, incurs the risk of contagious infection.